School of Science

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Browsing School of Science by Advisor "Chiguvare, Zivayi"

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    Design and performance evaluation of an oil/rock bed heat storage system for solar cooking
    (University of Namibia, 2025) Naule, Cecilia N.; Chiguvare, Zivayi
    This thesis presents the development and performance evaluation of a sensible thermal energy storage system that used sunflower oil and rock pebbles as heat storage mediums. The aim was to assess the system's performance based on charge and discharge rates, energy storage capacity, power output, cooking efficiency, and cost-effectiveness. The main body of the system was created with an old hot water geyser. An Arduino-based data logger was fabricated and was used to monitor and capture temperature changes throughout system operation periods. The data was analyzed with Python programming, from which time-temperature graphs were drawn. The heat retention capacity was obtained by heating the system to about 200 ยฐC and then cooling it, with the time taken to cool being recorded. The system took approximately 30 hours to cool from 194โ„ƒ to 60โ„ƒ. The system generated 0.028 kW of power and stored a total of 0.85 ๐‘˜๐‘Šโ„Ž of heat energy. The efficiency testing, which involved boiling five liters of water, yielded an average efficiency of 78.98%. The total cost of constructing the system was: N$ 3,860, with a unit energy cost of N$ 1.26/kJ and a unit power cost of N$ 137.86/W. The cooking test demonstrated that the system could simultaneously cook 300 g of rice in 43 minutes and 300 g of dry beans in about 4 hours using only the stored thermal energy. The study therefore concluded that the developed system was able to deliver a reliable and cost effective solution for domestic use. Nonetheless, constraints including insufficient funding for further development and a limited timescale, impeded comprehensive investigation of the system's capabilities. Future research needs to improve the design of the system as well as explore the possibility of using solar PV panels to heat the TES system
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    Hydrogen purity assessment using laser absorption Spectroscopy
    (University of Namibia, 2025) Shilongo, Rosamunde P.; Chiguvare, Zivayi
    Hydrogen purity assessment is a critical concern in energy applications, especially in fields involving hydrogen injection into natural gas pipelines and fuel cell research. This study addresses the limitations of current hydrogen measurement techniques by developing a novel hydrogen spectrometer (๐ป2-Spectrometer) based on direct Tunable Diode Laser Absorption Spectroscopy (d-TDLAS). The goal is to establish a traceable and accurate methodology for hydrogen purity and concentration measurement without relying on calibration gases. The main objective of this research is to develop and evaluate the performance of the ๐ป2-Spectrometer, specifically investigating its suitability for measuring hydrogen purity and hydrogen concentration in methane hydrogen mixtures. The study also aims to support hydrogen injection into natural gas pipelines by providing precise hydrogen concentration measurements. An experimental design was employed, utilizing the ๐ป2-Spectrometer to measure hydrogen line intensity and concentration. The measurements were taken for 99.999% pure hydrogen and hydrogen-methane gas mixtures to test the spectrometerโ€™s accuracy and reliability. The obtained data were compared against reference values from the HITRAN database and the certificate from the reference gas mix to evaluate performance. The findings revealed that the ๐ป2-Spectrometer demonstrated a significantly lower uncertainty of 1.6% in hydrogen line intensity measurements, compared to the 10% uncertainty reported in the HITRAN database. The measured line intensity obtained was 3.22 ร— 10โˆ’26 cm/molecule, which is slightly higher than the HITRAN value of 3.189 ร— 10โˆ’26 cm/molecule. In terms of hydrogen concentration, the spectrometer achieved an average mole fraction of 0.858 with a 1% uncertainty, closely aligning with the expected value of 0.900 as per the certificate from the reference gas mix with a 2% uncertainty. The ๐ป2 Spectrometer proved to be highly accurate and reliable, with potential applications in hydrogen quality control from electrolysis, fuel cell research, process control, and environmental monitoring. Its ability to provide traceable and precise measurements makes it a valuable tool for hydrogen-related research, optimizing system performance and ensuring compliance with regulatory standards